Pertused metal sheet



Nov. 29, 1938. E. A. COLBY 2,138,625

PERTUSED METAL SHEET Filed Aug. 7. 1930 2 Sheets-Sheet 1 ATTORNEYS Nov. 29, 1938. 'E. Av COLBY 2,138,525

PERTUSED METAL SHEET Filed Aug. 7. 1930 2 Sheets-Sheet 2 Patented Nov. 29, 1938 UNITED STATES PERTUSED METAL SHEET Edward A. Colby, Maplewood,'N. J., assignor to Baker & Company, Inc., a corporation of New Jersey Application August '7, 1930, Serial No. 473,730

2 Claims.

This inven'tionrelates to the provision of minute pertusions in ductile sheets of material by deformation of their surfaces'without change in weight. The invention is applicable ina minor degree for imparting rigidity to thin sheets of metal by indentation of its surface, but more particularly for the production of thin perforated sheets. for example, of a thickness of the order of foil, in which the face area of individual perforations is small and the total number of perforations per unit of surface area is large. It relates particularly to fine mesh screens of sheet material having greater accuracy, uniformity and permanency of mesh opening area than is possible in woven wire screens.

Another object is to provide fine screens from materials which cannot be drawn into wire form.

for weaving. There are many cases in which metal screens produced by this invention are particularly applicable, for'example, where uniformity of mesh openings, minimum weight of metal per unit of surface area, and rigidity of structure, are important factors. As one illustration, in one known method of producing nitric acid by the oxidationof ammonia, the mixture of air and ammonia gas is passed through fine mesh screens woven with platinum wire or alloys of the metal. Such screens vary in number of mesh openings from 45 to 150 per linear inch, and are woven with wire having a diameter from .0078 of an inch to .0016 of an inch. When the mixed gases in proper proportion come into contact with the platinum screen, chemical reaction takes place due to the catalytic action of platinum. As this action is exothermic, the platinum screens are raised to a high temperature from 700 to 900 C. This high temperature plus the pressure of rapidly flowing gases tends to distort the screens and alter the mesh opening. Since the chemical reactions take place at the surface of contact of the mixed gases with the platinum screen, it is most desirable to maintain uniformity of mesh opening and to so dispose the catalyzing metal as to expose to the gases the maximum surface of platinum per unit of its weight.

Theoretically, in the application of this type of catalyzer screen, both the area of the mesh openings and their boundary walls of platinum wire should be very small for a given volume of mixed gases passing. While woven wire screens are most generally used, manytrials of perforated sheet metal of relatively small surface area have been made, such screens comprising thin sheets of platinum'perforated by boring or punching small holes ther in of approximately .009 of an inch in diameter and spaced .015 of an inch on centers. In an 80 mesh woven platinum wire screen there are 6,400 mesh openings per square inch of surfacefthe area of each-opening with .003 inch diameter wire being .000089 of a square 5 inch. A round hole of this area would have a diameter of .0106 of an inch. 'l'o' bore or punch from thin sheet metal 6,400 holes of this diameter per square inch of surface is a most difficult and expensive operation, especially when the surface 10 area required runs into many hundreds of square inches for each screen.

Other objects are to provide novel and improved perforate sheets of ductile material in which the edges of the perforations have uniform extended side walls at one side of the sheet formed by the material displaced by the perforations, whereby the surface area of the perforate sheet is the same as or greater than that of the sheet before perforation thereof, and the sheets are reenforced against flexing to provide such sheets having a large number of uniformly shaped and spaced pertusions per unit of area so as to be suitable for use in many instances as a substitute for woven wire screens, for example as catalyzers in chemical processes and for grids and plates in electronic tubes. Grids and plates made by this process afford greater rigidity with less weight of metal for the same surface area than woven wire forms now used. Hum due to vibration of loosely crimped wires is eliminated by sheets embodying the invention, and the complete expulsion of gases occluded in metal parts by bombarding during evacuation of tubes is not limited by inequalities of electrical resistance and heat conductivity in right angularly disposed planes as is the case with woven wire screens. Other advantages and results of the invention will be brought out by the following description.

In the accompanying drawings I have shown one form of apparatus for carrying out my invention, but it should be understood that this is primarily for the purpose ,of illustrating the principles of the inventi n and that various other types of apparatus ay be utilized without departing from the spiritor scope of the'invention.

Referring to the accompanying drawings, in which corresponding and like parts are designated throughout the several views by the same a reference characters,

Figure 1 is a front elevation of one apparatus for producing. minute pertusions or deformations on the surfaces of sheets of ductile material, in accordance with my invention;

Figure 2 is an end elevation thereof;

Figure 3 is an enlarged fragmentary transverse vertical sectional view on the line 3-3 of Figure 1, showing the manner of passing the material between the rolls;

Figure 4 is a front elevation of the rolls illus- I trated in Figure 3;

Figure 5 is an enlarged fragmentary sectional view of the two rolls showing the manner of cooperation of the teeth and recesses in forming the pertusions;

Figure 6 is a fragmentary perspective view of a pertused sheet of material made in accordance with the invention;

Figure 7 is a vertical sectional view through the sheet;

Figure 8 is a top plan view ofa sheet of material which has been deformed, as for reinforcement, in accordance with the invention, and

Figure 9 is avertical sectional view on the line 9-9 of Figure 8. I

Specifically describing theembodiment of the invention illustrated in Figures 1-7, inclusive, the reference character A designates a steel cylinder or roll of the desired diameter and length, and which has on its periphery a plurality of teeth to cooperate with corresponding recesses in a second cylinder or roll B, in pertusing a sheet. The diameter of the rolls will vary in accordance with the thickness of the sheets to be operated upon and the number of pertusions desired for each unit of area, while the length of the rolls will vary with the width of the sheet to be produced.

In making the roll A, a cylinder of high grade steel, for example tool steel; has a spiral groove or thread I cut in its periphery of the desired .pitch, shape and depth, according to known machine shop methods. 1 The roll is then grooved longitudinally, as at 2, parallel to its axis, to form teeth 3, and preferably the longitudinal grooves or cross-cuts have the same shape, pitch and depth as the spiral thread I. The shape, pitch and depth will of course vary with the size and shape of the teeth desired; for example, if 80 teeth per linear inch or 6,400 teeth per square inch surface are desired,,the pitch will be .0125 of an inch. Preferably the teeth are polygonal in plan, for example substantially square, and generally pyramidal, as shown. After the roll has been so machined, it is hardened according to known processes.

The roll Bis made of softer material, or has a surface formed of softer material, than the roll A, and I have found copper mounted on a steel shaft to be very satisfactory. This roll B is formed with its'recesses by a rolling action under pressure between the two rolls A and B, which action may be performed in any suitable manner. As shown, the roll A may be mounted on a shaft 4 journaled in slide bearings 5 in a frame 6, while the roll B may be mounted on a shaft 1 mounted in slide bearings 8 in the frame. ,two shafts are geared together by pinions 9 and i0, and one of the shafts-may be rotated by a crank H. The two rolls are forced together into peripheral contact as by compression screws l2 engaging the slide bearings 5 of the shaft 4. With the rolls thus arranged the peripheralfaces are gradually forced together by the compression screws l2 while the rolls are rotated, and as the result the teeth 3 of the roll A are forced into the surface of the roll B so as to form recessesw The and alinement of the teeth and recesses are maintained extremely accurate.

In pertusing sheets of ductile material, for'example platinum, a sheet S is fed continuously between the rolls A and B which are continuously rotated in the proper direction, as indicated by arrows on Figure 3, and the rolls being pressed together the teeth 3 penetrate or pierce the sheet and force the displaced portions thereof into the recesses i3, as clearly shown in Figures 3 and 5, to form perforations or pertusions E30. These displaced portions i l form side walls for the corresponding perforations and project from one side of the sheet. Also these side walls are of an aggregate surface area substantially equal to the area of the corresponding perforations, and the perforated sheet thus remains of the same weight and aggregate surface area as an imperforate sheet of the same dimensions. It will be observed that the perforations will be uniformly spaced, and that a large number of perforations per unit of ,area can be produced.

Preferably the pertusions are rectangular faced, that is they are rectangular in shape on the surface of the sheet, and the aggregate face areas of said pertusions is substantially greater than the aggregate areas on the face of the sheet of the portions of the sheet between the pertusions, as shown in Figures 6 and 7. All portions of the sheet between the openings are substantially in the same common plane of the sheet, the openingsare uniform in size and regular in shape and the walls it are fiat, uniform and regular in shape; and apparently this is made possible by the firm support of the portions of the sheet between the openings, at all sides of the openings between the rollers during the pertusing operation, and the positive moving of the displaced portions M under control between the trated in Figure 5 of the drawings where the teeth are shown with convexly curved sides l5 whereby it is possible to obtain perforations of greater area for the same depth of penetration than would be possible with straight-sided teeth.

It will be observed that if the teeth should be formed with flattened apexes, or if the rolls should be separated to a greater-extent when passing the sheet therebetween, minute deformation without penetration of the sheet is possible,

' as illustrated in Figures 8 and 9 of the drawings,

where the deformation consists of a plurality of depressions l6 at one side of the sheet and corresponding projections I! at the other side. Such an operation results in hardening of the sheet and increases the rigidity or stiffness of very thin sheets of metal, especially in directions oblique to the rows of depressions; This operation is particularly advantageous where it is desired to obtain the maximum rigidity of extremely thin sheets of metal, without the perforation of the metal. Preferably, the sheet is cut into sections or piecesso'that the depressions are disposed obliquely or diagonally of the secons. r In the drawings, the perforations or pertusions I30 are shown as approximately square and pro-- duced by teeth, the pitch of which in the two planes at right angles is the same. Should the pitch of the teeth in the two planes differ, the pertusions would have unequal sides. As clearly shown in Figures 3 and 5 of the drawings, the

material is penetrated by the points of the individual teeth and then split into the four triangular-shaped segments or displaced portions M which have their apexes at the point of penetration. These four triangular-shaped segments are by proper shaping of the individual teeth spread apart as the rolling operation is completed, so that each pertusioii has practically a uniform cross-section from base to apex. The sheet thus produced has one smooth fiat side, while the other side is covered with several thousand triangular projections l4 per square inch of surface area. Assuming that the sheet of material is .001 of an inch in thickness, these triangular projections extend about .008 of an inch above the side of the sheet. Accordingly, when the sheet is tobe used as a catalyzer in nitric acid production processes, the surface for contact between the metal and gases is greater by the area of these triangular projections than is attainable with woven wire screens of the same weight. Therefore, other conditions being equal, the cost of catalyzing metal per ton of nitric acid produced is less with this form of perforated sheet screen than with a woven wire screen.

Also, sheets of metal made according to the invention may be used in making grids and plates for electronic tubes, providing greater rigidity with less weight of material for the same-sufface area than is possible in the forms now used; and the hum due to vibration of crimped wires now used is eliminated, while the complete expulsion of occluded gases in the metal is facilitated. Sheets embodying the invention have uniform electrical resistance and heat conductivity, and the sheets may be rolled or bent without breaking, which are especially desirable characteristics in the manufacture of electrodes for electronic tubes.

From the foregoing it will appear that the invention provides a perforated sheet metal screen of the order of woven wire screens formed of wire of from, for example, about .0078 to about .0016

of an inch in diameter, and having. from several;

uniform in all directions, and has an aggregate surface area equal to or greater than that of an unpertused sheet of the same dimensions. invention thus provides a perforate sheet having a minimum of material, a maximum of surface area and a maximum ofrigidity which is uniforfn in all directions, such as is highly desirable especially in electrodes for electronic tubes and in catalyzer screens.

1 Having thus described the invention, what I claim is: v a

1. A sheet of ductile metal of any thickness up to approximately four thousandths of an inch provided with from approximately one thousand to sixty four hundred pertusions per square inch, the metal displaced to form the pertusions projecting integrally and angularly from the sheet to' increase the rigidity and strength of the sheet. 2. A sheet of ductile noble metal of a thickness not exceeding approximately'four thousandths ofan inch provided with at least approximately one thousand pertusions per square inch having side walls formed of the metal displaced to form the pertusions projecting integrally and angularly from the sheet to increase the rigidity of the sheet.

EDWARD A. COLBY.

The 

